# -*- coding: utf-8 -*-
"""
Created on Mon May 27 11:08:31 2024

@author: Administrator
"""
"""
x = float(input("请输入x的值："))
if x >= 90:
    grade = "A"
elif x >= 80 and x < 90:
    garde = "B"
elif x >= 70 and x < 80:
    garde = "C"
elif x >= 60 and x < 70:
    garde = "D"
else:
    garde = "E"
print("对应的等级是:",grade)

"""
a = float(input("a = "))
b = float(input("B = "))
c = float(input("c = "))

if a + b > c and b + c > a and a + c > b:
    p = (a + b + c)/2
    area = (p * (p - a) * (p - b) * (p - c)) ** 0.5
    print("三角形的面积是：%.3f" % area)
    